This application claims the priority of German application 197 42 444.9-14, filed in Germany on Sep. 26, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for manufacturing a hollow body from two metal bars, and more particularly to a process in which the metal bars are flatly disposed on one another, comprising the steps of introducing high pressure fluid within a closed internal high-pressure forming tool into a parting line between the metal bars; widening the metal bars until they are placed on a die sinking contour of the forming tool defining a final shape of the hollow body, while they form the hollow body; welding the metal bars to one another by beam welding in a welding-through; trimming the thus-formed metal bar composite by a cutting operation; and cutting off a fluid inlet area of the metal bar composite after the widening.
DE 195 35 870 A1 describes a process in which two flat sheet metal blanks are placed on one another and are clamped in an internal high-pressure tool between the top tool and the bottom tool. After the closing of the forming tool, a pressure fluid is guided under high pressure into the parting line, after which the blanks (bars) expand and are placed corresponding to the contours against the die sinking of the forming tool. After the expansion, the bars are laser-welded to one another in the clamped state. Subsequently, the pressure fluid is relaxed and is guided out of the forming tool; the bar composite is removed from the forming tool and is then, on the side of the weld seam facing away from the expansion, trimmed by a laser cutting tool. The pressure fluid inlet area is also cut off. Finally, in its end form, the thus-produced oblong hollow body has a flange on both longitudinal sides which extends along these sides.
The flange produced in this known process is very disadvantageous for the further installation or mounting of the hollow body, for example, as a part of a frame structure of a motor vehicle body in terms of the space-frame technology because of the required installation space. A cutting-off of the flange is not useful because the hollow body will disintegrate into two half shells which can then be connected at high expenditures and with the loss of the desired overall structure. Thus, manufacturing of a flangeless hollow body cannot take place in a secure manner.